Carburetor choke

ABSTRACT

A carburetor assembly has a primary passage to supply a lean mixture to main combustion chambers of an engine, and has an auxiliary passage to supply a rich mixture to auxiliary combustion chambers of the engine. A throttle valve in each passage is provided with a shaft, and linkage connects the two shafts for coordinated motion. A choke valve in the primary passage is connected to the primary throttle valve so that positioning of both the primary throttle valve and the auxiliary throttle valve are affected when the choke valve is in operation. Structure is provided to limit opening movement of the choke valve to different extents, depending on the ambient temperature at the time of starting the engine.

[451 Sept. 24, 1974 1 CARBURETOR CHOKE [75] Inventors: Toshimasa Shishido, Tokyo; Minoru Atsumi, Kawagoe, both of Japan [73] Assignee: Honda Giken Kogyo Kabushiki Kaisha, Tokyo, Japan 22 Filed: July 30,1973

21 Appl. No.: 383,785

[52] US. Cl. 123/75 B, 123/32 ST, 123/119 F,

123/127 [51] Int. Cl. F02b 3/00, F02m 13/04, F02m 23/04 [58] Field of Search 123/75 B, 32 ST, 119 F, 123/127 [56] References Cited UNITED STATES PATENTS 2,121,920 6/1938 Mallory 123/75 B 3,066,662 12/1962 May at al. 123/75 B 3,092,088 6/1963 Goossak et al... 123/75 B 3,124,113 3/1964 May et al. 123/75 B 3,364,911 1/1968 Baudry et al.. 123/75 B 3,406,667 10/1968 Evans et al 123/32 ST 3,439,658 4/1969 Simonet 123/32 ST 3,543,736 12/1970 Suzuki et al 123/32 ST R26,603 6/1969 Seggern et al 123/75 B Primary Examiner-Wendell E. Burns Attorney, Agent, or Firm-Lyon & Lyon [5 7 ABSTRACT A carburetor assembly has a primary passage to supply a lean mixture to main combustion chambers of an engine, and has an auxiliary passage to supply a rich mixture to auxiliary combustion chambers of the engine. A throttle valve in each passage is provided with a shaft, and linkage connects the two shafts for coordinated motion.- A choke valve in the primary passage is connected to the primary throttle valve so that positioning of both the primary throttle valve and the auxiliary throttle valve are affected when the choke valve is in operation. Structure is provided to limit opening movement of the choke valve to different extents, depending on the ambient temperature at the time of starting the engine.

8 Claims, 9 Drawing Figures T p l 7 l mmwsarzmn CARBURETOR CHOKE This invention relates to internal combustion piston engines in which each cylinder is provided with a main combustion chamber and an auxiliary combustion chamber, the chambers being connected by a torch nozzle. An engine of this type is disclosed in the copending application of date et al. Ser. No. 353,786 filed Apr. 23, 1973 and entitled Reduction of N HC, and CO in the Exhaust Gases of Internal Combustion Engines."

More specifically, this invention relates to a choke for a carburetor assembly which has a primary passage for supplying a lean mixture to the main combustion chambers and an auxiliary passage for supplying a rich mixture to the auxiliary combustion chambers. It is important that the air-fuel ratios of the lean mixture and the rich mixture be maintained within close limits for all operating conditions of the engine, Including startup conditions. This is necessary in order to avoid the production of unwanted pollutants in the exhaust gases of the engine. Reference is made to Applicants copending application Ser. No. 383,784 entitled Carburetor" and filed of even date herewith. The present invention is concerned with a choke valve apparatus which finds particular usefulness in connection with the carburetor disclosed in that application.

When the choke valve is used during engine start-up operations, an increase in richness of the air-fuel mixture occurs in the primary passage, and a change in flow rate occurs in both the primary and auxiliary passages, the flow rate increasing substantially in the auxiliary passage which does not contain a choke valve. The degree of the required changes in richness and flow rate depends upon the ambient temperature; the colder the ambient temperature the greater the degree of change in richness and in flow rate.

In accordance with this invention, structure is provided which limits the extent of opening of the choke valve in accordance with ambient temperature. Thus, when ambient temperature is normal, the apparatus permits opening of the choke valve to an intermediate position between fully closed and fully open. However, when the ambient temperature is cold, for example below about 60 F., the apparatus further restricts the maximum opening of the choke valve so that it opens only to a small extent.

The choke valve mechanism may be operated either manually or automatically.

Another important feature of this invention is to cause the choke valve mechanism to control the degree ofopening ofthe auxiliary throttle valve. During engine start-up operations, much of the air delivered to the engine passes through the auxiliary passage because there is no choke valve in the auxiliary passage. Consequently, it is important to control the extent of opening of the auxiliary throttle valve in accordance with the operation of the choke valve mechanism, and this control must be reasonably precise and accurate in order to avoid the production of unwanted pollutants in the exhaust gases of the engine during start-up conditions.

Other and more detailed objects and advantages will appear hereinafter.

In the drawings:

FIG. 1 is a side elevation partly broken away and partly in section showing a preferred embodiment of this invention. The choke valve is shown fully open.

FIG. 2 is a plan view partly broken away showing the parts in the same position as FIG. 1.

FIG. 3 is a side elevation similar to FIG. 1 but showing certain of the parts in an intermediate position.

FIG. 4 is a side elevation similar to FIG. 1 showing the parts in position corresponding to partially closed position of the choke valve.

FIG. 5 is a sectional detail taken substantially on the lines 55 as shown in FIG. 1.

FIG. 6 is a side elevation partly broken away showing a modification, certain parts being omitted for clarity of illustration.

FIG. 7 is a sectional side elevation taken substantially on the lines 77 as shown in FIG. 6.

FIG. 8 is a sectional detail taken substantially on the lines 88 as shown in FIG. 6.

FIG. 9 shows a modified form of vacuum breaker equipped with a damper.

Referring to the drawings, the carburetor assembly generally designated 1 has a primary passage 2 for delivering a lean air-fuel mixture to the main combustion chambers of an internal combustion engine. The carburetor assembly also has an auxiliary passage 3 for delivering a rich air-fuel mixture to the auxiliary combustion chambers of the engine. The passage 2 has a venturi throat 4 and is provided with a throttle valve 5 connected to a throttle shaft 6 and actuator 7. Similarly, the auxiliary passage 3 has a venturi throat 8 and is provided with a throttle valve 9 connected to a throttle shaft 10 and actuator 11. The two throttle shafts 6 and 10 are connected for coordinated movement by means of arms 12 and 13 and link 14.

A choke valve 16 is mounted in the passage 2 upstream from the venturi throat 4 and is mounted on a shaft 17 mounted to turn on the carburetor body 18. A stationary sleeve 19 projects from the carburetor body and encircles a portion of the choke shaft 17. A choke actuator member 20 has a hub portion 21 mounted to turn on the stationary sleeve 19 and is provided with a socket 210 for reception of a terminal fitting 22 provided on the end of the control cable 23. An arcuate groove 24 provided on the member 20 receives the control cable 23. A torsion spring 25 encircles a hollow hub 26 formed integrally on a carburetor body 18. The hub 26 and the stationary sleeve 19 function as a single integral unit. One end of the torsion spring 25 is fixed to the stationary stop pin 27, and the other end engages the stop finger 28 provided on the actuator member 20.

The control cable 23 slides within an enclosing tube 30 and is secured to a slide rod 31 having a manual knob 32 fixed to one end. The rod 31 projects through an opening in the stationary wall 33 and the parts 34 and 35 serve to clamp the stationary tube 30 with respect to this wall 33. From this description it will be understood that when the knob 32 is manually grasped and moved to the left as viewed in FIG. 1, the cable 23 moves the actuator member 20 in a clockwise direction against the force of the torsion spring 25.

Also mounted to turn on the stationary sleeve 19 is the crank member 37 having an arm 38 pivotally connected at 39 to the rod 40. The member 37 also has an arm 41 engaging a return tab 42 on an element 43 fixed to the choke shaft 17. A second torsion spring 44 encircles the hub portion of the actuator member 20 and has one end 45 engaging the element 43 and the other end 46 engaging the actuator member 20. The action of the torsion spring 44 is to move the element 43 and choke shaft 17 in a clockwise direction with respect to the actuator member 20, as viewed in FIG. 1.

A cam surface 49 is formed on the actuator member 20 and this cam surface cooperates with two separate follower elements. As shown in FIGS. 3 and 4, the follower element 51 is fixed on the motion limiter member 52 mounted to turn on a stationary pin 53. The limited member 52 also carries a stop element 54 which cooperates to limit counterclockwise movement of the projection 55 on the member 37. A torsion spring 56 has one end engaging the limiter member 52 and the other end engaging a stationary pin 57a, so that the torsion spring 56 acts to move the member 52 in a clockwise direction to hold the follower element 51 in contact with the cam surface 49.

A second follower element 57 engages the cam surface 49 and this follower element 57 is mounted on a lever 58 pivoted at 59 and having a rounded end 60 engageable with the finger 61 fixed on the throttle valve actuator 7. A torsion spring 62 acts to maintain the follower element 57 in contact with the cam surface 49. From this description it will be understood that turning movement of the actuator member 20 to the position shown in FIG. 3 serves to cause the lever 58 to move in a counterclockwise direction against the action of the torsion spring 62 and thereby cause the actuator 7 to move the throttle valve clockwise from closed position.

The rod 40 connects the pivot 39 on the member 37 to the moving part 63 of the vacuum breaker assembly generally designated 64. A flexible diaphragm 65 cooperates with the wall 66 to form an expansible chamber 67. This chamber 67 is connected through port 68 to a suction passage 69 and 70 leading to a region of manifold vacuum pressure. When the engine is running, the vacuum pressure in the intake manifold is reflected through passage 69 to the expansible chamber 67. A compression spring 72 acts on the central portion 63 of the diaphragm 65 in a direction to enlarge the volume of the chamber 67.

The purpose of the vacuum breaker 64 is to move the choke valve 16 in an opening direction as soon as the engine turns under its own power after initial cranking. Thus, when the engine is at rest and atmospheric pressure exists in chamber 67, the compression spring 72 expands the diaphragm chamber 67 and moves the rod 40 to the left from the position shown in FIG. 1. When the engine turns under its own power, the vacuum pressure in the chamber 67 moves the flexible diaphragm 65 to the position shown in FIG. I, compressing the spring 72 and moving the choke valve 16 to a certain extent which is regulated by the stop element 54, depending on ambient temperature. The finger 61 on the primary throttle valve actuator 7 rests against the adjustable stop screw 15.

When the ambient temperature is not cold, for example above 60 F., and the engine is to be initially started after a period of non-use, the operator of the vehicle grasps the knob 32 and pulls it to the left, as viewed in FIG. 1, until the spring loaded ball 73 enters the detent 74 in the rod 31. This brings the actuator member and limited 52, as well as lever 58 and throttle valve 5, to the position shown in FIG. 3. As soon as the engine starts to turn on its own power, the vacuum pressure in the chamber 67 moves the flexible diaphragm against the action of the spring 72 to the position shown in FIG. 3. This movement causes the rod 40 to swing the member 37 to the position shown in FIG. 3. The choke valve 16 is then held in an intermediate position. As soon as the engine warms up, the operator of the vehicle returns the knob 32 to the position shown in FIG. 1, and the choke valve 16 returns to its fully open position.

If the ambient temperature should be cold, for example below about 60 F., the vehicle operator pulls the choke knob 32 and moves it to its maximum extent, when the finger 28 on the actuator 20 engages the stationary pin 27. The actuator 20, limiter 52, lever 58 and throttle valve actuator 7 are then in the position shown in FIG. 4. After initial cranking and when the engine turns under its own power, the member 37 is moved by the vacuum breaker and its rod 40 until the projection 55 contacts the stop element 54 on the limiter 52. The choke valve 16 is then in the position shown in FIG. 4. After the engine has warmed up, the vehicle operator returns the knob 32 to the position shown in FIG. 1, at which time the choke valve 16 returns to its fully open position.

It will be noted that for each position of the choke valve 16, both the primary throttle valve 5 and the auxiliary throttle valve 9 are moved to positions to assure best operating characteristics of the engine consistent with minimizing unwanted pollutants in the exhaust gases.

In the modified form of the invention shown in FIG. 9, the vacuum breaker 64 is supplemented by a damper device 75. This device includes a flexible diaphragm 76 having a central portion fixed to the movable part 63 to define a liquid chamber 77 of variable volume and between the wall 78 and the diaphragm 76. A restricted passageway 79 connects the chamber 77 to the reservoir 80. Movement of the rod 40 and part 63 is damped by the dash-pot action of hydraulic liquid passing through the orifice 79. The damping action is greatest when the liquid is cold, and decreases when the liquid viscosity changes as the liquid warms up. An adjustable stop 81 may be provided to limit the motion of the rod 40 and moving part 63 to the right, as viewed in FIG. 9.

In the modified form of the invention shown in FIGS. 6, 7 and 8, the choke assembly is operated automatically instead of manually. The choke valve 86 in the primary passage 87 is mounted on the shaft 88. The shaft 88 projects through a stationary hollow hub 89 projecting from the carburetor body 90. A conventional bimetal assembly 91 having a spiral bimetal element 92 therein is mounted on the carburetor body. The spiral bimetal element 92 is connected at one end to an arm 93 of a connector member 94 fixed to a projecting end of the choke shaft 88. A conventional electric heater 95 is included in the assembly 91. Changes in temperature cause the bimetal element 92 of the device 91 to apply a force to the arm 93 of the member 94 and tending to turn the choke valve 86 within the passage 87.

The bimetal assembly 91 is omitted from FIG. 6 of the drawings for clarity of illustration, only an end portion of the bimetal element 92 being shown.

A member 96 mounted to turn on the hollow station ary hub 89 has a first arm 97 pivotally connected to the rod 97a, leading to a vacuum breaker assembly (not shown) which is similar to either the type shown in FIGS. l-3 or the type shown in FIG. 9. The member 96 also has a projection 98 which is positioned to contact any one of a plurality of steps 99, 100 or 101 on the cam member 102. This cam member is mounted to turn on a stationary pin 103 provided on the carburetor body 90. A bimetal element 104 is attached at one end to the cam member 102 and at the other end to the stationary pin 105.

A cam member 107 is mounted to turn on the hollow hub 89 and a portion of this member is provided with arcuate steps 108 and 109. A projection 110 on the rocker member 112 is positioned to engage either of these arcuate steps 108 or 109. A torsion spring 111 has one end secured to the member 107 and the other end is secured to the member 94-.

The rocker member is pivotally mounted at 113 and is provided with an arm 114 pivotally connected to one end of a link 115. The other end of the link 115 is pivotally connected to crank arm 116 provided on the actuator 117. This actuator 117 is fixed to the shaft 118 for the primary throttle valve 119 below the venturi throat 120 in the primary passage 87. Although the auxiliary passage and the auxiliary throttle valve are omitted from the drawings in FIGS. 6, 7 and 8, it is to be understood that these parts are present in this form of the invention and that linkage means similar to that previously described is used to coordinate the turning movements of the primary throttle valve and the auxiliary throttle valve.

In the operation of the form of the invention shown in FIGS. 6, 7 and 8, the conventional bimetal assembly 91 and its conventional internal electric heater 95 act to position the arm 93 and choke valve 86, depending upon the temperature of the spiral bimetal element 92.

When the engine is to be started and when the ambient temperature is cold, for example below 60 F., the choke valve 86 is in closed position and the other parts of the device are positioned as shown in the drawings. During initial cranking of the engine, air drawn downward through the primary passage 87 acts to move the choke valve 86 toward open position, because of the eccentric mounting of the choke valve 86 with respect to its supporting shaft 88. This turning movement ofthe choke valve 86 and shaft 88 in a counterclockwise direction as viewed in FIG. 6 takes place against the resilient spring action of the bimetal strip 92 and against the force of the torsion spring 111. When the engine starts, the vacuum breaker rod 97a is pulled to the right causing the member 96 and its arm 97 to move in a counterclockwise direction. The projection 980 contacts the step surface 99 on the member 102 to limit the extent of opening movement of the choke valve 86. As the engine warms up, the bimetal strip 104 causes the member 102 to turn in a counterclockwise direction so that the projection 98a moves down to step 100 and then to step 101.

The projection 110 on the rocker member 112 frictionally engages the step surface 108, and as the bimetal assembly warms up to permit counterclockwise movement of the member 107, the projection 110 moves from the step 108 down to step 109 and through other additional steps until the choke valve 86 is in fully open position. This movement of the projection 110 and the member 112 is communicated through the link to the arm 116 of the principal throttle valve actuator 117.

The arm 121 on the member 84 and the arm 122 on the member 112 cooperate to serve as an unloader mechanism should the engine become flooded during the starting period. This mechanism partially opens the closed choke valve 86 to allow increased air flow to reduce the richness of the air-fuel mixtures. This is accomplished by depressing the accelerator pedal so that the throttle valves are widely opened. When this is done, the arm 122 is brought into contact with the arm 121 to force the choke valve 86 to a partly open position. The additional air leans out the fuel mixture enough to permit the engine to start.

Having fully described our invention, it is to be understood that we are not to be limited to the details set forth herein but that our invention is of the full scope of the appended claims.

We claim: I

1. In a carburetor assembly, the combination of: means forming a primary passage adapted to supply a lean mixture to a main combustion chamber of an engine, means forming an auxiliary passage adapted to supply a rich mixture to an auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means mounting said shafts for turning movement, means coordinating the turning movements of said shafts, a choke valve mounted to turn in said primary passage upstream from the throttle valve therein, means including a shaft for actuating said choke valve, and means for moving the primary throttle valve in accordance with movement of the choke actuating means, whereby movement of the choke actuating means serves to move both the primary throttle valve and the auxiliary throttle valve.

2. A carburetor assembly for use with an internal combustion engine having at least one main combustion chamber and an auxiliary combustion chamber connected thereto by a torch nozzle, said carburetor assembly having, in combination: a primary passage adapted to supply a lean mixture to the main combustion chamber of the engine, an auxiliary passage adapted to supply a rich mixture to the auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means for coordinating turning movements of said shafts, a choke valve in said primary passage upstream from the throttle valve in that passage, means for actuating said choke valve, and means for moving the main throttle valve in response to movement of said actuating means, whereby movement of the actuating means for the choke valve causes movement of both of the throttle valves.

3. A carburetor assembly for use with an internal combustion engine having at least one main combustion chamber and an auxiliary combustion chamber connected thereto by a torch nozzle, said carburetor assembly having, in combination: a primary passage adapted to supply a lean mixture to the main combustion chamber of the engine, an auxiliary passage adapted to supply a rich mixture to the auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means for coordinating turning movements of said shafts, said means including an arm connected to turn with each of said shafts, respectively, a link pivotally connected to each of said arms, a choke valve in said primary passage upstream from the throttle valve in that passage, means for actuating said choke valve and means for moving the primary throttle valve in response to movement of said actuating means, whereby movement of the actuating means for the choke valve causes movement of both of the throttle valves.

4. A carburetor assembly for use with an internal combustion engine having at least one main combustion chamber and an auxiliary combustion chamber connected thereto by a torch nozzle, said carburetor assembly having, in combination: a primary passage adapted to supply a lean mixture to the main combustion chamber of the engine, an auxiliary passage adapted to supply a rich mixture to the auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means for coordinating turning movements of said shafts, said means including an arm connected to turn with each of said shafts, respectively, a link pivotally connected to each of said arms, means for adjusting the angular position of one of the arms with respect to its respective shaft, a choke valve in said primary passage upstream from the throttle valve in that passage, means for actuating said choke valve and means for moving the primary throttle valve in response to movement of said actuating means, whereby movement of the actuating means for the choke valve causes movement of both of the throttle valves.

5. The combination set forth in claim 4 in which the adjusting means is provided for the arm associated with the auxiliary throttle shaft.

6. In a carburetor assembly, the combination of: means forming a primary passage adapted to supply a lean mixture to a main combustion chamber of an engine, an auxiliary passage adapted to supply a rich mixture to an auxiliary combustion chamber of an engine, each of the passages having a throttle valve therein carried on a shaft, means mounting said shafts for turning movement, means coordinating the turning movements of said shafts, a choke valve mounted to turn in said primary passage upstream from the throttle valve therein, means including a shaft for actuating said choke valve, said choke actuating means including a member mounted to turn about the axis of the choke shaft, said member having a cam surface thereon, and means ineluding a follower engaging the cam surface for moving the primary throttle valve in accordance with movement of said member.

7. In a carburetor assembly, the combination of: means forming a primary passage adapted to supply a lean mixture to a main combustion chamber of an engine, means forming an auxiliary passage adapted to supply a rich mixture to an auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means mounting said shafts for turning movement, means coordinating the turning movements of said shafts, a choke valve mounted on a shaft to turn in said primary passage upstream from the throttle valve therein, a choke actuating member mounted to turn about the axis of the choke shaft, said member having a cam surface thereon, a limiter mounted to turn about an axis spaced from the choke shaft, a follower on the limiter engaging the cam surface, a rotary member mounted to turn about the axis of the choke shaft and having an element engageable with the limiter, a vacuum breaker connected to actuate said rotary member, and means including a follower engaging the cam surface for moving the primary throttle valve in accordance with movement of said choke actuating member.

8. In a carburetor assembly, the combination of: means forming a passage adapted to supply an air-fuel mixture to an internal combustion engine, a throttle valve mounted to turn in the passage, a choke valve mounted on a shaft to turn in said passage upstream from the throttle valve therein, a member mounted to turn about the axis of the choke shaft, means for coordinating the movements of the choke shaft and throttle valve, a temperature responsive member connected to turn the choke shaft, a limiter mounted to turn about an axis spaced from the choke shaft, temperature responsive means for turning said limiter, a rotary member mounted to turn about the axis of the choke shaft, said rotary member having an element engageable with the limiter to limit the extent of turning movement of said rotary member, means whereby said rotary member limits the turning movement ofthe choke shaft, and a vacuum breaker connected to actuate said rotary member. 

1. In a carburetor assembly, the combination of: means forming a primary passage adapted to supply a lean mixture to a main combustion chamber of an engine, means forming an auxiliary passage adapted to supply a rich mixture to an auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means mounting said shafts for turning movement, means coordinating the turning movements of said shafts, a choke valve mounted to turn in said primary passage upstream from the throttle valve therein, means including a shaft for actuAting said choke valve, and means for moving the primary throttle valve in accordance with movement of the choke actuating means, whereby movement of the choke actuating means serves to move both the primary throttle valve and the auxiliary throttle valve.
 2. A carburetor assembly for use with an internal combustion engine having at least one main combustion chamber and an auxiliary combustion chamber connected thereto by a torch nozzle, said carburetor assembly having, in combination: a primary passage adapted to supply a lean mixture to the main combustion chamber of the engine, an auxiliary passage adapted to supply a rich mixture to the auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means for coordinating turning movements of said shafts, a choke valve in said primary passage upstream from the throttle valve in that passage, means for actuating said choke valve, and means for moving the main throttle valve in response to movement of said actuating means, whereby movement of the actuating means for the choke valve causes movement of both of the throttle valves.
 3. A carburetor assembly for use with an internal combustion engine having at least one main combustion chamber and an auxiliary combustion chamber connected thereto by a torch nozzle, said carburetor assembly having, in combination: a primary passage adapted to supply a lean mixture to the main combustion chamber of the engine, an auxiliary passage adapted to supply a rich mixture to the auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means for coordinating turning movements of said shafts, said means including an arm connected to turn with each of said shafts, respectively, a link pivotally connected to each of said arms, a choke valve in said primary passage upstream from the throttle valve in that passage, means for actuating said choke valve and means for moving the primary throttle valve in response to movement of said actuating means, whereby movement of the actuating means for the choke valve causes movement of both of the throttle valves.
 4. A carburetor assembly for use with an internal combustion engine having at least one main combustion chamber and an auxiliary combustion chamber connected thereto by a torch nozzle, said carburetor assembly having, in combination: a primary passage adapted to supply a lean mixture to the main combustion chamber of the engine, an auxiliary passage adapted to supply a rich mixture to the auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means for coordinating turning movements of said shafts, said means including an arm connected to turn with each of said shafts, respectively, a link pivotally connected to each of said arms, means for adjusting the angular position of one of the arms with respect to its respective shaft, a choke valve in said primary passage upstream from the throttle valve in that passage, means for actuating said choke valve and means for moving the primary throttle valve in response to movement of said actuating means, whereby movement of the actuating means for the choke valve causes movement of both of the throttle valves.
 5. The combination set forth in claim 4 in which the adjusting means is provided for the arm associated with the auxiliary throttle shaft.
 6. In a carburetor assembly, the combination of: means forming a primary passage adapted to supply a lean mixture to a main combustion chamber of an engine, an auxiliary passage adapted to supply a rich mixture to an auxiliary combustion chamber of an engine, each of the passages having a throttle valve therein carried on a shaft, means mounting said shafts for turning movement, means coordinating the turning movements of said shafts, a choke valve mounted to turn in said primary passage upstream from the throttle valve therein, means including a shaft for actuating said choke valve, said choke actuating means including a member mounted to turn about the axis of the choke shaft, said member having a cam surface thereon, and means including a follower engaging the cam surface for moving the primary throttle valve in accordance with movement of said member.
 7. In a carburetor assembly, the combination of: means forming a primary passage adapted to supply a lean mixture to a main combustion chamber of an engine, means forming an auxiliary passage adapted to supply a rich mixture to an auxiliary combustion chamber of the engine, each of the passages having a throttle valve therein carried on a shaft, means mounting said shafts for turning movement, means coordinating the turning movements of said shafts, a choke valve mounted on a shaft to turn in said primary passage upstream from the throttle valve therein, a choke actuating member mounted to turn about the axis of the choke shaft, said member having a cam surface thereon, a limiter mounted to turn about an axis spaced from the choke shaft, a follower on the limiter engaging the cam surface, a rotary member mounted to turn about the axis of the choke shaft and having an element engageable with the limiter, a vacuum breaker connected to actuate said rotary member, and means including a follower engaging the cam surface for moving the primary throttle valve in accordance with movement of said choke actuating member.
 8. In a carburetor assembly, the combination of: means forming a passage adapted to supply an air-fuel mixture to an internal combustion engine, a throttle valve mounted to turn in the passage, a choke valve mounted on a shaft to turn in said passage upstream from the throttle valve therein, a member mounted to turn about the axis of the choke shaft, means for coordinating the movements of the choke shaft and throttle valve, a temperature responsive member connected to turn the choke shaft, a limiter mounted to turn about an axis spaced from the choke shaft, temperature responsive means for turning said limiter, a rotary member mounted to turn about the axis of the choke shaft, said rotary member having an element engageable with the limiter to limit the extent of turning movement of said rotary member, means whereby said rotary member limits the turning movement of the choke shaft, and a vacuum breaker connected to actuate said rotary member. 